This invention relates generally to devices and methods for delivering a selected medication or other therapeutic fluid to a patient at a subcutaneous infusion site. More particularly, this invention relates to an improved medication infusion set of the type having a soft or flexible cannula adapted for subcutaneous placement, in combination with an infusion needle associated with a protective shroud plate to minimize risk of patient contact therewith while providing a high strength and unidirectional releasible coupling with the cannula.
Medication injection or infusion sets are generally well known in the art, to include a relatively soft and flexible cannula providing a transcutaneous pathway through which a selected medication or other therapeutic fluid can be administered to a patient at a selected subcutaneous site. In a common form, the soft cannula is carried by a compact housing to include a resilient self-sealing septum mounted at an upstream end of the cannula. This cannula housing is initially assembled with an insertion needle extending through the septum and cannula, wherein the insertion needle is manipulated to pierce the patient's skin to place the cannula transcutaneously, followed by withdrawal of the insertion needle to leave the soft cannula in place on the patient. The selected medication is then coupled to the cannula, typically by means of a length of infusion tubing connected to a medication source, to deliver the medication through the cannula to the patient. In one configuration, the infusion tubing is connected to the cannula housing at a location downstream from the septum as shown, for example, in U.S. Pat. Nos. 4,755,173; 5,176,662; and 5,257,980. In another arrangement, the infusion tubing is coupled to the cannula housing by means of an infusion needle passed through the septum as shown, for example, in U.S. Pat. No. 5,522,803.
Subcutaneous infusion sets of the above-described type are used extensively to administer medication to a patient over an extended period of time. For example, such infusion sets are used with medication infusion pumps of the type described in U.S. Pat. Nos. 4,562,751; 4,685,903; 5,080,653; and 5,097,122 for delivering a long-term medication such as insulin in a continuous or programmable dosage to the patient. With such medication delivery systems, however, it is known that the medication source must be periodically disconnected from the cannula. For example, it has been recognized that the infusion set should be replaced every few days, whereby it is necessary for the patient to uncouple the medication source from an in situ cannula upon removal thereof from the patient, and to recouple the infusion tubing with a second, newly placed cannula. In addition, some patients may briefly disconnect the medication source and related infusion tubing from the cannula to facilitate certain activities, such as swimming or bathing, or participation in certain athletic activities, etc.
In this regard, an optimal medication infusion set is adapted for low profile and inobtrusive placement on the patient, while permitting quick and safe periodic disconnection from and reconnection to the medication source. To this end, use of an infusion needle adapted for coupling through the self-sealing septum provides a quick and easy structure for connecting and disconnecting the medication source from the cannula, but also subjects the patient to undesirable needle sticks from exposure to the infusion needle. Moreover, this arrangement requires a strong and reliable mechanical interlock between the cannula housing and the infusion needle to insure consistent and proper interengagement without inadvertent component separation, while permitting quick and easy and repeated disconnection when desired. All of these features are desirably provided in an infusion set constructed from relatively simple and preferably disposable components which can be manufactured in a cost-efficient manner from medical grade plastic or the like.
The present invention provides an improved medication infusion set designed to meet these features and advantages, by including an infusion needle associated with a protective shroud plate. The shroud plate closely overlies and substantially encases the infusion needle in a manner minimizing risk of patient contact therewith, while additionally providing a strong guide structure for keyed or one-way interconnection with a cannula housing.